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EP-4735660-A1 - PRODUCTIVE COATING PROCESS FOR A STEEL SHEET, CORRESPONDING EQUIPMENT, A METALLIC COATED HOT ROLLED STEEL SHEET

EP4735660A1EP 4735660 A1EP4735660 A1EP 4735660A1EP-4735660-A1

Abstract

A method for manufacturing a coated steel sheet comprising the following steps: a. Providing a steel sheet (10), b. Descaling said steel sheet by acid pickling, c. Feeding said descaled steel sheet into a pressurized chamber (3) above the atmospheric pressure, said pressurized chamber comprising an inlet (2), and being connected via at least one sealing lock (20) to at least one vacuum deposition chamber (4), d. Depositing a metallic coating layer by vapor deposition at a sonic speed, wherein a gas is blown into the pressurized chamber (3) to keep it at a pressure above atmospheric pressure, said gas being released through the inlet (2).

Inventors

  • GAILLY, ERIC
  • AMIMI, NAUWFEL
  • SILBERBERG, ERIC
  • PACE, Sergio
  • RUWET, Vincent

Assignees

  • ArcelorMittal

Dates

Publication Date
20260506
Application Date
20240614

Claims (15)

  1. 1. A method for manufacturing a coated steel sheet comprising the following steps: a. Providing a steel sheet (10), b. Descaling said steel sheet by acid pickling, c. Feeding said descaled steel sheet into a pressurized chamber (3) above the atmospheric pressure, said pressurized chamber comprising an inlet (2), and being connected via at least one sealing lock (20) to at least one vacuum deposition chamber (4), d. Depositing a metallic coating layer by vapor deposition at a sonic speed, wherein a gas is blown into the pressurized chamber (3) to keep it at a pressure above atmospheric pressure, said gas being released through the inlet (2).
  2. 2. The method according to claim 1 wherein the pressurized chamber (3) has a pressure from 10 to 20 000 Pa above the atmospheric pressure.
  3. 3. The method according to claims 1 or 2, wherein in step d) the metallic coating has a thickness from 2.0 to 75.0 pm per side.
  4. 4. The method according to anyone of claims 1 to 3, wherein a metallic primer layer with a thickness from 2 to 15 nm is deposited on the steel sheet after step c) and before step d).
  5. 5. The method according to anyone of claims 1 to 4, wherein the steel sheet is a hot rolled steel sheet.
  6. 6. An equipment for the manufacturing of a coated steel sheet comprising the following units through which the steel sheet is successively driven: a. A pickling unit (1 ) allowing the removal of scale on the surface of said steel, b. A pressurized chamber (3) having an inlet (2) and being connected to a sealing lock (20), c. At least one jet vacuum deposition chamber (4), said equipment comprising means for blowing a gas in the chamber (3) to keep it above atmospheric pressure, said gas being released outside the pressurized chamber through the inlet (2).
  7. 7. An equipment according claim 6 comprising means for continuously monitoring the pressure inside said pressurized chamber (3) and means for adjusting the gas flow rate blown in said chamber according to said monitored pressure.
  8. 8. An equipment according to claims 6 or 7 comprising a unit for metallic primer deposition by magnetron sputtering after said pressurized chamber (3) and before said vacuum deposition chamber (4).
  9. 9. An equipment according to anyone of claims 6 to 8, wherein the at least one vacuum deposition chambers comprises two or more ejectors.
  10. 10. A metallic coated hot rolled steel sheet, comprising successively: - A hot rolled steel sheet, - An oxide layer in contact with said sheet having a thickness from 3 to 60 nm and being mainly composed of iron oxides, - A metallic coating having a thickness from 2.0 to 75.0 pm per side.
  11. 11. A metallic coated hot rolled steel sheet according to claim 10 comprising a metallic primer layer with a thickness from 2 to 15 nm between said oxide layer and said metallic coating.
  12. 12. A metallic coated hot rolled steel sheet according to claim 11 , wherein the metallic coating is a monolayer coating and has a thickness from 2.0 to 7.5 pm.
  13. 13. A metallic coated hot rolled steel sheet according to claim 11 , wherein the metallic coating is a multilayer coating and has a thickness from 10.0 to 75 pm.
  14. 14. A metallic coated hot rolled steel sheet according to anyone of claims 10 to 13, wherein the metallic coating consists of zinc and residual impurities coming from the manufacturing process up to 0.1 weight %.
  15. 15. A metallic coated hot rolled steel sheet according to anyone of claims 10 to 13, wherein the metallic coating comprises from 0.5 to 40 weight % magnesium, residual impurities coming from the manufacturing process up to 0.1 weight %, the balance being zinc.

Description

PRODUCTIVE COATING PROCESS FOR A STEEL SHEET, CORRESPONDING EQUIPMENT, A METALLIC COATED HOT ROLLED STEEL SHEET The present invention deals with the vacuum coating of steel. Metallic coating of steel sheets is currently performed by hot dipping in a metallic bath. Immediately above the bath, liquid metal is wiped by gas knives to adjust coating thickness. In the case of a galvanizing line, the steel sheet must be heated from 500 to 550°C to pass in the metal bath while avoiding zinc solidification before the gas knives. The coating thickness range of conventional hot dip coating technology is limited by the process. Bare spots may appear at the lower limit if the wiping pressure is excessive, or liquid metal dripping if the wiping pressure is insufficient at the upper limit of the coating thickness range. Furthermore, it is impossible to hot dip again a coating layer because the metal coating would melt. Vacuum coating is the deposition of a source material, for example, from the crucible of a vacuum evaporator, on a substrate to form germs (nucleation), which gradually develop (growth) and result in an ordered coating layer. Vacuum coating process is not limited regarding the thickness of the coating deposited. Vacuum deposition can be performed by several successive steps to increase the coating thickness. When coating by vacuum deposition, heating the steel close to the metal bath temperature is not needed anymore. This allows significant energy and CO2 emissions savings compared to hot dip coating. It is known from the prior art to coat a cold rolled steel sheet by vacuum deposition. The surface of the cold rolled steel needs to be cleaned to ensure a proper adhesion of the coating. Especially when oil or organic residues remain on the cold rolled steel, the coating adhesion will be impaired and bare spots or cracks may appear. In recent years, the applications for hot rolled steels are increasing in the fields of automotive and general industry. Hot rolled steels offers applications where a high corrosion resistance is needed, for examples chassis parts of automobile or in agricultural environment. It also offers application where a minimal corrosion resistance is needed. In other words, the thickness of the corrosion protection needed for hot rolled steels is wide. However, in the case of the hot rolled steel, the surface is covered by a mill scale resulting from the contact of hot steel with air at the hot rolling mill. Said scale is composed of iron oxides which are layered. The thickness of the scale is from 0.5 to 8 mm. It is porous and brittle and must be removed prior to coating, else the coating wouldn’t adhere to the hot rolled steel. The patent CN 113846291 discloses a cleaning and coating-plating combined unit for a galvanized steel sheet and a production method of the cleaning and coating-plating combined unit. The plasma cleaning can not only realize the descaling of a hot rolled sheet, but also realize the surface cleaning of a cold rolled sheet. However, cleaning by plasma is slow. It is known to use plasma to remove a thin oxide layer of several nanometer. For removing the hot rolling scale of at least 500 nm, the plasma descaling will last longer. On a continuous process, this will require to slow the line speed below the coating deposition speed. The vacuum chamber must be longer compared to a vacuum chamber only dedicated to coating. The resulting equipment is expensive, and its productivity is limited by the line speed necessary for descaling. A simple and productive process to perform the vacuum coating of both hot rolled and cold rolled steel by is therefore needed with the corresponding equipment. A first object of the present invention is to provide a manufacturing method to produce a coated steel sheet by vacuum deposition. This object is achieved by the method of claims 1 to 8. A second object of the present invention is to provide an equipment able to produce a coated steel sheet by vacuum deposition. This object is achieved by the equipment of claims 9 to 13. A third object of the present invention is to provide a coated hot rolled steel sheet. This object is achieved by the steel sheet of claims 14 to 18. The invention will now be described in detail with reference to the figure 1 showing an equipment according to the invention. A first object of the invention is achieved by a method for manufacturing a steel sheet comprising the following steps: a. Providing a steel sheet 10, b. Descaling said steel sheet by acid pickling, c. Feeding said descaled steel sheet into a pressurized chamber 3 above the atmospheric pressure, said pressurized chamber comprising an inlet 2, and being connected via at least one sealing lock 20 to at least one vacuum deposition chamber 4, d. Depositing a metallic coating layer by vapor deposition at sonic speed, wherein a gas is blown into the pressurized chamber 3 to keep it at a pressure above atmospheric pressure, said gas being released thr